Roadside assistance for Mars Rover

Getting your car stuck is irritating enough, but what do you do when your vehicle is dug into the sand of another planet and the nearest auto club is 180 million miles away?

If you're the Jet Propulsion Laboratory, you bring Mars down to Earth.

In May, the Mars rover Spirit became embedded in a patch of fluffy Martian soil, the worst such incident in the more than five years that Spirit and its twin, Opportunity, have been exploring the planet's equatorial region.

Since then, engineers have been trying to figure out the best way to extricate the rover, a project that has come to be known at the La Canada Flintridge laboratory as the "Free Spirit" program. T-shirts are being made to memorialize the effort to liberate the rover.

This week, scientists finished replicating the situation on Mars in a 30-foot-square workroom, mixing together 5,400 pounds of diatomaceous earth and clay to produce a fine, powdery mixture the color of creme brulee and as fluffy and light as flour. Now comes the task of trying to free a test vehicle, the so-called Earth Rover, to figure out what might work for Spirit.

"This isn't the same as we have on Mars," cautioned Paolo Bellutta, a rover team member, about the powder. "Diatomaceous earth is made of fossils, and we have no evidence of fossils on Mars."

But it is the closest thing to the soil on Mars, rover project manager John Callas said.

The engineers drove the Earth Rover, about 5 feet tall by 7 feet wide, into an 8-by-12-foot sandbox. By Wednesday, it was stuck -- its six wheels embedded in 5 inches of the Martian soil analogue. After sloping the sand so that the test rover was pitched on its side to match Spirit's predicament, the engineering team pronounced itself satisfied that it had succeeded in marooning two rovers on two planets.

The trick now, Callas said, is to put together a series of maneuvers on Earth that can be applied on Mars.

The first technique, which engineers intend to apply next week, is to ask the rover to simply drive forward. Because it has a gimpy right front wheel, Spirit has been driving backward in recent years, dragging the wheel along. Commanding the rover forward would amount to backing out of the fluffy sand patch onto surer ground nearby.

"We think terrain we can drive on is just a few feet away," Callas said.

He said that although Spirit is embedded, he doesn't believe it is truly stuck. This may sound like a subtle difference, but Callas says it's crucial to the outcome of the Free Spirit effort.